Non-invasive aeromechanical methods will be used to study various aspects of normal speech breathing and speech breathing disorders. Four primary investigations will be conducted. The first investigation will document the nature of the emergence of normal speech breathing in infants and young children and provide a data base against which infants and young children with speech breathing disorders can be compared. The second investigation will test the hypothesis that laryngeal airway resistance during vowel production decreases with age and thereby leads to the development of compensatory adjustments of the breathing apparatus. The same investigation also will provide normative data needed to enhance the clinical evaluation and management of voice disorders in adults of all ages. The third investigation will elucidate the mechanism involved in speech breathing disorders in individuals with Parkinson's disease. This investigation will expand understanding of the impact of neuromotor impairments on speech production and contribute information of value for application to the evaluation and management of persons with parkinsonism. The fourth investigation will test the effects of abnormal trussing on speech breathing in individuals with abdominal paresis or paralysis resulting from spinal cord injury. Data from this investigation will have a direct impact on strategies for the clinical management of speech breathing control in individuals with neuromotor impairments affecting abdominal muscle control. Applications of the four investigations mentioned should extend to various disorders caused by neuromotor dysfunction, including cerebral palsy, spinal cord injury, poliomyelitis, myasthenia gravis, spinal muscular atrophy, peripheral neuropathy, muscular dystrophy, and others.